Monday, October 24, 2011

Please give rating and comments

Your star ratings and comments on my apps will be both encouraging and helpful.


If you have never seen a Sudoku puzzle. You have never flipped through newspapers in the past few years. This Japanese originated puzzle has enjoyed worldwide attention.

The rules are extremely simple: fill up the grid using 1-9. Each digit must only be used once in each row, column, or the neighbor mini-grid. Each puzzle yearns a solution. I am not good at solving such puzzles... it takes a lot of trial and errors and it is ideal work for the computer.

Decent computer science students should have some idea how to solve this immediately upon seeing such puzzle. Real programmers should be able to crank one out in a few hours. This is just like the 8-queens back-tracking problem if we are to solve this using some trial-and-error approach.

Indeed, there are many such solvers on the Android market, and on the web. A few years ago I have written this program in command line, reading a puzzle in text file, then converted to java applet. I recently ported this to Android. That solver code is untouched, just the UI is different.

Get yours here

Tuesday, October 18, 2011

Math Experiments

I had a dream, way back, perhaps a decade ago, before there were anything remotely looking like ipads: "One day learning will be evolved by interactive books"

My original vision was PDF files can be embedded with little programs, like there are some movable elements in children's books.

I accumulated a decade of programming into this app: Math Experiments.

These are originally written as java applets accompanying my book.

I converted the helpless applets into Android. Applets are now warned with yellow bars or won't run at all. Applets are so 1990s. However, android view programming has a lot of same ideas as applets... and android can do more, even OpenGL 3D graphics (which my little math experiments do not require).

So now you can enter your own parameters and experiment with it. How I so much want a calculator to do fractions for me when I was doing drills in elementary school. I long hoped to play interactively with the parameters that move the sine wave (like the knobs on the oscilloscope) and parabola.

The limit as h->0 can now be shown visually out of imagination. yippee.

Get yours free
at the Android Market